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Brazilian doctors are seeing unusual new health problems among infants born to mothers who contracted the Zika virus. The complications often go beyond those seen when other infections cause microcephaly. (Published Wednesday, Oct. 12, 2016)

Researchers are trying to infect mosquitoes in Brazil and Colombia with a type of bacteria that could prevent them from spreading the Zika virus and other dangerous diseases.

British and American governments are teaming up with the Bill and Melinda Gates Foundation and the U.K.-based Wellcome Trust to expand field tests in Rio de Janeiro in Brazil and the city of Bello in northwest Colombia, philanthropist Bill Gates told a conference Wednesday.

The tests revolve around the Wolbachia genus of bacteria, which has been shown to hamper the spread of viruses when it's carried by mosquitoes. The virus doesn't occur naturally in Aedes aegypti — the tropical mosquitoes primarily responsible for spreading viruses such as Zika, yellow fever, dengue fever and chikungunya — but researchers have spent more than 10 years working to coax the bacteria into infecting that particular breed of insect in a bid to derail the diseases it carries.

In an interview with The Associated Press, Gates said the $18 million roll-out would finally test whether the concept can work.

"We'll know within a year, if these mosquitoes we've released, if they're becoming common amongst the population," he said. "Then we'll see simply by the number of people who get sick from either Zika or dengue. If those numbers come down quite substantially in these cities but not in other cities that'll be the proof of this over a decade-long quest to use this intervention."

In a statement, the Eliminate Dengue campaign said the roll-out in Latin America follows earlier field trials in Australia, Vietnam and Indonesia as well as small-scale work in Brazil and Colombia dating back to 2014.

Zika was initially known only to cause flu-like symptoms in some people but has since attracted global concern after a surge of cases in babies born with small heads in northeast Brazil. The virus has since been linked to a birth defect known as microcephaly and become a leading public health worry.

In his AP interview, Gates also spoke about polio— he hopes next year will mark the last reported case of the disease — and the British exit from the European Union, which he said probably wouldn't be dramatic for U.K. science but "could create a little bit of uncertainty and disruption."

5 Facts About the Zika Virus

The first known case of Zika virus in a human was discovered in 1952 in Uganda and Tanzania, but a recent outbreak that drew international attention to Brazil began in 2015. Since then the virus has spread rapidly across the Americas. Here are some basic facts about Zika and some tips for protecting yourself if you are in an affected area. (Published Wednesday, Sept. 14, 2016)

Finally, the billionaire Microsoft co-founder poured cold water on talk of a turn toward U.S. politics.

Gates, who was identified in leaked emails as being among those Hillary Clinton's campaign considered for vice president last spring, gave an emphatic "Nope, not me" when asked whether Americans should expect to see his name on the ballot in 2020.